1. Field of the Invention
The present invention relates to a seating sensor system for determining whether the seat of a vehicle is occupied by a person, and an industrial vehicle provided with the seating sensor system.
2. Description of the Related Art
A vehicle (including a passenger car and an industrial vehicle) provided with a seating sensor system for determining whether a seat is occupied by a person is conventionally known. Such a seating sensor system comprises a switch to be turned on (or off) by the pressure on the seating place of a seat, and if a person sits on the seat, the switch is turned on (or off). Then, a vehicle is controlled based on the state of this switch. Specifically, for example, if it is determined that a seat is not occupied by a person, an air bag system corresponding to the seat is not operated.
As a technology for improving the accuracy of determining whether a seat is actually occupied by a person, a system which has pressure sensors not only in the seating place of a seat but also at the back of the seat is known (for example, see Patent Document 1). This system determines whether a seat is occupied by a person using those sensors.
Patent Document 1: Japanese Patent Publication No. 9-127258 (FIG. 4 and paragraph 0063)
However, in the conventional seating sensor system, if the switch or sensor fails or if a signal from the switch or sensor is not transmitted to a control device controlling a vehicle, it cannot be determined whether a seat is occupied by a person. In this case, when a seat is not occupied by a person, it is wrongly determined that the seat is occupied and the vehicle is controlled accordingly. Conversely, when the seat is actually occupied by a person, it is wrongly determined that the seat is not occupied and the vehicle is controlled accordingly.
In the configuration disclosed by the Patent Document 1, when one of the two sensors, one of which is located in the seating place and the other one of which is located at the back of the seat, fails, it can be detected the failure. However, if a plurality of sensors (or switches) is provided, it is difficult to realize the cost reduction of the entire seating sensor system. In addition, even in the configuration disclosed in the Patent Document 1, if a signal from the switch or sensor is not transmitted to the control device, there is no way of determining whether a seat is occupied by a person.